This invention relates to impact printers and specifically to the character carrying elements, print-carrier or type-carrier elements used in impact printers. The invention is specifically concerned with a new and improved type-carrier element as an article of manufacture and with a method of making same.
In impact printers, there is typically utilized a rotatable print disc, barrel, thimble, or the like comprising a type-carrier element and a hub mounting arrangement. The type-carrier element has a plurality of flexible spaced-apart radially-distributed finger or arm members with print characters thereon. These arms are disposed at angular increments around a center portion which is designated to be rotatably mounted in the impact printer. The print carrying arms are positioned in the printer so as to be generally parallel to the plane of a surface which is to receive the printing such as a sheet of paper. To print any desired character, the type-carrier element is rotated by a driving mechanism in the printer to a position corresponding to the selected print character on one of the arms. The character is then printed by hammering the arm into contact with an inked ribbon and against the paper.
The rotatable type-carrier element may, as indicated above, take various forms such as discs, barrels, thimbles, and the like. One of the more popular forms is the planar disc-shaped element used in the print disc commonly referred to as the "daisy wheel". Another is referred to as a "thimble" because of its thimble-like appearance in which a center portion carries the spaced arms extending generally upwardly therefrom. Herein, all of these various types and styles of carrier elements are recognized as including a center portion having a plurality of arms extending peripherally therefrom, whether in the same plane as the center portion or angularly thereto. Such elements are referred to collectively herein as print-carrier or type-carrier elements. In use, the element itself consisting of the center portion and radially extending arms may be fitted with various kinds of hub fittings and the like for rotatably mounting the element, indexing it, and so forth. The present invention is specifically concerned with the type-carrier element itself and its fabrication.
Typical prior art type-carrier elements make use of type character or type slugs which are integrally molded at the ends of the arms. Various portions of the carrier elements, sometimes both the arms and the type or print character slugs may be made of thermoplastic materials. In some of the prior art elements, the arms are formed from metal and the character slugs are molded plastic formed on or attached to the arm ends. The slugs carry the type characters for printing and are sometimes covered with a metalized surface coating for increased life. Metal slugs have also been used by welding them to the arm ends individually. Composite structures of plastic and metal suffer from relatively short life. Typical problems due to the use of plastics are arm breakage and character face degradation. Welded carrier elements formed completely of metal have not been used successfully because of their relatively high weight and high inertia.
It is an object of this invention to provide rotatable metal print-carrier elements of one-piece, having integrally formed print characters thereon.
It is another object of this invention to provide type-carrier elements which possess extended useful life.
It is another object of the invention to provide all-metal print-carrier elements of low inertia and low weight.
It is also an object of the invention to provide a method of making such type-carrier elements, particularly by a method wherein a one-piece element of metal is made in such a manner as to avoid having stresses therein.
These and other objects of the invention will become more apparent from the description hereinbelow which sets forth a method of making type-carrier elements wherein a negative photoresist material is used.